Certain aircraft are convertible. They have multiple configurations; one configuration for transporting passengers and another alternative configuration for transporting freight. Such aircraft is converted from one configuration to the other in short time to obvious advantage. Convertibility allows the aircraft to be more fully utilized, essentially around the clock in one configuration or another as needed to meet the demands of the transportation marketplace. One such convertible aircraft, as example, is the McDonnell Douglas MD-11 aircraft.
As is familiar to those boarding an aircraft to obtain passenger service, the aircraft contains rows of seats for seating passengers, paneling on the side walls, a ceiling, overhead compartments, a galley, flight attendant's control panel, and all other accouterments of the passenger configuration. One also finds passenger doors located on each side of the aircraft's rear through which the passenger may embark, and debark the airplane. The freighter configuration, however, is not too familiar, if at all, to the lay person. When the passenger period is complete, the craft may be used for freight shipments for another period of time and it is converted to the freighter configuration. The passenger seats are removed; the ceiling, wall paneling, and cooking galley are removed; and the overhead equipment control panels and the attendant's passenger door control switches are removed, and cargo rollers are installed over the floor to yield a large hollow shell for warehousing freight.
Freight carried on pallets is introduced through the aircraft's freight door, a door located at the front of the plane that is rarely seen by or even known to most passengers. Those loaded pallets are pushed to the rear of the plane. Additional loaded pallets follow and are positioned along side, continuing until the plane's cabin is completely filled with freight. As is apparent, when the craft is in the freighter configuration there seems little need to use any passenger doors. The removal of the flight attendant's passenger door control switches and associated circuit breakers located in the passenger cabin, that allowed a flight attendant to open and close the passenger doors during passenger configuration, until now, seemed of no material consequence.
Should one wish to access the aircraft through the passenger door while in the freight configuration, the door may be opened with an emergency air bottle. However, use of the air bottle is not routine and is impractical. The air bottle is an emergency tool designed for "one time" operation, and it only opens a single door. Hence, its use for routine door operation is not practical.
One also might wish to raise and lower the passenger door attendant to converting the aircraft from the passenger configuration to the freight configuration. As example in some recent aircraft decorating arrangements, one finds that although the passenger accouterments and the flight attendant's passenger door control switches may be removed, it is not possible to remove the trim around the passenger door frame without first opening the passenger door. In such a situation the airline personnel are faced with a "catch 22" situation. They cannot remove some parts of the craft's interior if the door is in its raised, that is, open position, and cannot remove the door trim if the door is in its closed position. Such a situation would require complex maneuvering by those airline personnel charged with transforming the aircraft's configuration that is both time consuming and requires undertaking a non-traditional procedure. The desire remains to strip the passenger cabin of the passenger accouterments so that the cargo can be loaded.
The door could be forced open using several strong persons, but that is not a safe method. Or the flight attendant's door control switches and the associated overhead equipment panels, removed during the re-configuration procedure can be replaced, operated to raise the door, the door trim removed, the door lowered again, and the flight attendant's switches and overhead equipment panels removed again, a second time. In the MD-11 aircraft, as example, approximately three and one-half hours is required to re-install and then remove those flight attendant passenger door switches. Such is a time consuming procedure, that not only increases operational costs, but could result in unintended delays in flying the aircraft. A need thus exists in such limited circumstances for an alternative method of operating the aircraft's motorized passenger doors without the necessity of reinstalling the flight attendant's control panel and overhead equipment panel.
An object of the invention therefore is to provide a novel passenger door control apparatus that emulates the functions of a flight attendant's control panel and the associated equipment panel.
A further object of the invention to provide a portable easily transportable electrical apparatus that may be temporarily installed, quickly and easily, aboard aircraft to permit operation of the passenger doors when the aircraft is in the freight configuration.
As an example, the Md-11 convertible freighter aircraft may be changed in configuration to transport passengers or to transport freight. The passenger doors on that craft are electrically operated and contain a number of safety mechanisms to ensure that the door is not damaged by the opening and closing movements. A release solenoid is provided that essentially locks the door in place, preventing unintended door movement. Before the door can be either raised or lowered, the release solenoid must first be operated to unlock the door. To open, the door is elevated or raised by means of an electrically controlled motor mechanism. To close, the electrical motor mechanism, lowers the door. Additionally, position limit switches are properly positioned relative to the door to break the electrical power circuit to the motor when the door attains a prescribed limit position during each of the opening and closing operations. Those limit switches prevent the door from moving past the prescribed limit positions during either opening or closing.
For freighter configuration the cabin attendant door control panel and overhead circuit breaker equipment panels that contain the number 2 and 3 left and right passenger door control circuits are removed to make room for cargo. The removal of that equipment and control renders the number 2 and 3 passenger doors inoperative.
The respective passenger door motor, open/close limit switches, and release solenoids, which remain in place in both aircraft configurations, require electrical power and proper operational sequencing to operate the electric motor driven cable mechanism to raise and/or lower the door. The motor driven cable mechanism pulls the door up a track to a position above the door opening in the side of the aircraft, the door open position; and lowers the door down the track to the door closed position.
A specific object of the invention, thus, is to permit passenger door operation of an Md-11 aircraft when the aircraft is in the freighter configuration while retaining the safety features provided by the door's upper and lower position limit switches.